University of Groningen
Advanced tuning algorithms for high-frequency SIS mixers Hesper, Ronald; Barkhof, Jan; Vos, Tobias; Baryshev, Andrey
DOI:
10.5281/zenodo.3240311
IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below.
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Publication date: 2019
Link to publication in University of Groningen/UMCG research database
Citation for published version (APA):
Hesper, R., Barkhof, J., Vos, T., & Baryshev, A. (2019). Advanced tuning algorithms for high-frequency SIS mixers. Paper presented at ALMA Development Workshop, ESO 2019, Garching, Germany.
https://doi.org/10.5281/zenodo.3240311
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Advanced Tuning Algorithms
for
High-Frequency SIS Mixers
Ronald Hesper
Jan Barkhof
Tobias Vos
Andrey Baryshev
ALMA Development Workshop, ESO 2019-06-05 NOVA Sub-mm
Instrumentation Group
Tuning SIS mixers
The main tuning parameters of SIS mixers:
● Bias voltage (V
SIS)
● Bias current (I
SIS), set by LO power (VD)
● Josephson suppression, set by magnetic field (I
M)
ISIS(VD)
VSIS Josephson
Josephson suppression
Ideal Reality: multiple states, hysteresis
Delivered tunings: usually 2nd minimum
Significant noise temperature
improvement possible in many (most?) mixers going to first minimum
Software infrastructure
Top-level structure Structure of instrument sub-package
The engineering software package (“Rodrigo”) used for Band 9 and Band 5
qualification is not suitable as-is for adaptive algorithms (no conditionals or loops). → new Python-based engineering package (“NOVAsoft”)
● Maintains “look & feel” of Rodrigo (configuration, file formats, basic scripts)
● ... but unlocks full programming language facilities
Automating human decisions
Formerly, the minima were found by eye. The new algorithm finds them by filtering and differentiating, within limiting values.
There are several parameters to tweak in order to get reliable identification of minima → should be tested on sufficient #mixers The suppression can be verified by the p-p range of the Josephson structure in the power curve.
How many mixers can be improved?
By how much?
For CHAMP+ upgrade ≈20 AlN SIS junctions were re-measured
In both 1st and 2nd minima (sometimes 3rd)
Expected improvement for ALMA
At the high end of the band (e.g., CO 6-5), about 10-15% noise temperature could be shaved off →5-7 antennas for free!
H-field dependence of the
noise temperature
Question: what actually determines the noise temperature:
● The magnetic field?
● The supercurrent? 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Bias voltage [mV] 32.5 30.0 27.5 25.0 22.5 20.0 17.5 IF power [dBm] Pol 0 (8.8 mA) Pol 0 (7.8 mA) Pol 1 (11.4 mA) Pol 1 (6.4 mA)
As long as the bias voltage stays out of the Josephson region, there is a straight relationship between TN and IM, no sign of minima.
T
N
vs. I
M
Discrepancy between CHAMP data and recent measurements Tuning? To be investigated
10-2 10-1 100 101 102 103 tau (sec.) 10-8 10-7 10-6 10-5
Allan Variance Total power for different magnet currents Polarisation 0 Im = 0.0 mA Im = 4.0 mA Im = 8.0 mA Im = 12.0 mA Im = 16.0 mA Im = 20.0 mA Im = 24.0 mA 10-2 10-1 100 101 102 103 tau (sec.) 10-8 10-7 10-6 10-5
Allan Variance Total power for different magnet currents Polarisation 1 Im = 0.0 mA Im = 4.0 mA Im = 8.0 mA Im = 12.0 mA Im = 16.0 mA Im = 20.0 mA Im = 24.0 mA
Do other performance properties
suffer from low magnet current?
50 100 150 200 250 300 350 400 Load (K) 0.9 0.95 1 1.05 1.1
Normalized Gain vs. Load Temperature Imagnet 0.0 mA 50 100 150 200 250 300 350 400 Load (K) 0.9 0.95 1 1.05 1.1
Normalized Gain vs. Load Temperature Imagnet 2.0 mA 50 100 150 200 250 300 350 400 Load (K) 0.9 0.95 1 1.05 1.1
Normalized Gain vs. Load Temperature Imagnet 4.0 mA 50 100 150 200 250 300 350 400 Load (K) 0.9 0.95 1 1.05 1.1
Normalized Gain vs. Load Temperature Imagnet 6.0 mA 50 100 150 200 250 300 350 400 Load (K) 0.9 0.95 1 1.05 1.1
Normalized Gain vs. Load Temperature Imagnet 8.0 mA 50 100 150 200 250 300 350 400 Load (K) 0.9 0.95 1 1.05 1.1
Normalized Gain vs. Load Temperature Imagnet 10.0 mA 50 100 150 200 250 300 350 400 Load (K) 0.9 0.95 1 1.05 1.1
Normalized Gain vs. Load Temperature Imagnet 12.0 mA 50 100 150 200 250 300 350 400 Load (K) 0.9 0.95 1 1.05 1.1
Normalized Gain vs. Load Temperature Imagnet 14.0 mA 50 100 150 200 250 300 350 400 Load (K) 0.9 0.95 1 1.05 1.1
Normalized Gain vs. Load Temperature Imagnet 16.0 mA 50 100 150 200 250 300 350 400 Load (K) 0.9 0.95 1 1.05 1.1
Normalized Gain vs. Load Temperature Imagnet 18.0 mA 50 100 150 200 250 300 350 400 Load (K) 0.9 0.95 1 1.05 1.1
Normalized Gain vs. Load Temperature Imagnet 20.0 mA 50 100 150 200 250 300 350 400 Load (K) 0.9 0.95 1 1.05 1.1
Normalized Gain vs. Load Temperature Imagnet 22.0 mA 50 100 150 200 250 300 350 400 Load (K) 0.9 0.95 1 1.05 1.1
Normalized Gain vs. Load Temperature Imagnet 24.0 mA
